Method for charging lithium ion secondary battery

A method for charging a lithium ion secondary battery by constant current constant voltage (CCCV) charging, comprising:

• a step of performing constant current (CC) charging up to a predetermined set voltage;
• and a step of switching to constant voltage (CV) charging after the set voltage is reached, thus performing charging while reducing charging current so as to keep the set voltage, wherein the lithium ion secondary battery is composed using a negative electrode material containing Si, thereby having characteristics such that, during a period of the CC charging, a transition point Ta appears in a temperature rise gradient when temperature of the battery rises along with progression of the charging, and with the transition point Ta being a border, a temperature rise gradient in an initial T1 period is steeper than a temperature rise gradient in a T2 period following the T1 period, changeover time ts is set in a range of tT≦ts≦(tT×1.2), based on charging time tT corresponding to timing at which the transition point Ta appears after start of the CC charging from a condition of the SOC of 0%, obtained by measurement in advance, a charge state of the lithium ion secondary battery is determined before start of the charging, and during a period of the CC charging, when the charge state is before the transition point Ta, the CC charging is performed at a first current value until the changeover time ts elapses from start of the charging, and after the changeover time ts elapses, the CC charging is performed at a second current value larger than the first current value, and when the charge state exceeds the transition point Ta, the CC charging is performed at a second current value larger than the first current value.